C# ConvertAll syntax

Question

I'm trying to understand the syntax for ConvertAll in C#, and despite looking at several examples and trying to copy them, I can't get the following line containing s2 to compile; VSE2013 says

"Error 1 No overload for method 'ConvertAll' takes 1 arguments ".

what does the error message mean? Where am I going wrong? And yes, I understand that Select is much better to use in these situations, for several reasons. Thanks!

static int Main(string[] args)
{ 
    Console.WriteLine ("jello world");

    int s1 = args.Sum(st => int.Parse(st));
    int s2 = args.ConvertAll(x => int.Parse(x)).Sum();
    int s3 = args.Select(st => int.Parse(st)).Take(2).Sum();
    return 0;
}

Maybe if you explain what you're trying to do? – JamesSugrue Apr 09 '15 at 04:30 — JamesSugrue, Apr 09 '15 at 04:30

score 2 · Answer 1 · answered Apr 09 '15 at 04:31

You are calling ConvertAll on an actual array instance - but ConvertAll is a static method, hence does not have access to the content of your array - you need to pass in the array itself as the first parameter so that it can use it - and since it's a static method should call it on the Array class itself:

int s2 = Array.ConvertAll(args, x => int.Parse(x)).Sum();

Also shorter using a method group:

int s2 = Array.ConvertAll(args, int.Parse).Sum();

score 1 · Answer 2 · answered Apr 09 '15 at 04:31

1

Change args.ConvertAll(x => int.Parse(x)).Sum(); to Array.ConvertAll(args, x => int.Parse(x)).Sum();.

As the error message told you, 'ConvertAll' does not take 1 argument, so that should clue you in to the fact that you need more arguments (in this case, the array).

See MSDN for proper usage of Array.ConvertAll.

answered Apr 09 '15 at 04:31

Amy S

31
4

Thanks for your comments; I had already found that syntax, but there are numerous examples out there showing the form int[] s2 = args.ConvertAll (delegate converter ) ; is that deprecated now ? – user3150422 Apr 09 '15 at 15:28
Are you sure those examples weren't with lists, rather than arrays? That is the proper syntax for lists. See the difference in examples [here](https://msdn.microsoft.com/en-us/library/kt456a2y(v=vs.110).aspx). – Amy S Apr 09 '15 at 20:24
You're right, and that was my basic problem: I thought args was a list, when it was an array. Thanks! If I convert it to a list with: List list = args.OfType().ToList(); then I can sum it with int ss = list.ConvertAll(x => int.Parse(x)).Sum(); – user3150422 Apr 10 '15 at 01:58
Glad you got it figured out! – Amy S Apr 10 '15 at 06:09

C# ConvertAll syntax

2 Answers2